It has been previously suggested (Maryanski, et al., 1994) that three-dimensional aspects of tissue-equivalent, polymer-gel dosimeters, combined with the flexibility and high resolution inherent in magnetic resonance imaging, can provide radiation dose distributions in a manner that is unique to the field of radiation oncology. Tomographic analysis of an irradiated polymer gel can yield important dosimetry data for the new and highly complex treatment modalities which are being introduced into radiation oncology such as stereotactic radiosurgery, conformal radiation therapy, the dynamic wedge, scanning electron beams and energy-modulated proton beams. While MRI will likely remain the method of choice at some institutions for specific types of studies, for many institutions there will be significant financial, administrative and logistical advantages to have a relatively low-cost tomographic dosimetry system located in the radiation oncology department which can readily provide the bulk of the clinical and research data required by the radiation oncology physicists.